/*
*    Qizx/open 3.0 beta
*
* This code is the open-source version of Qizx.
* Copyright (C) 2004-2009 Axyana Software -- All rights reserved.
*
* The contents of this file are subject to the Mozilla Public License 
*  Version 1.1 (the "License"); you may not use this file except in 
*  compliance with the License. You may obtain a copy of the License at
*  http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
*  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
*  for the specific language governing rights and limitations under the
*  License.
*
* The Initial Developer of the Original Code is Xavier Franc - Axyana Software.
*
*/
using System;
using ExprDisplay = System.Qizx.XQuery.ExprDisplay;
using ModuleContext = System.Qizx.XQuery.ModuleContext;
using XQType = System.Qizx.XQuery.XQType;
namespace System.Qizx.XQuery.Op
{
	
	public abstract class UpdatingExpr:Expression
	{
		public override int Flags
		{
			get
			{
				return UPDATING;
			}
			
		}
		public int mode;
		public Expression what; // inserted nodes, new name, new value
		public Expression where; // 
		
		public UpdatingExpr():base()
		{
		}
		
		public override Expression Child(int rank)
		{
			return rank == 0?what:where;
		}
		
		public static bool isUpdating(Expression e)
		{
			return e != null && (e.Flags & UPDATING) != 0;
		}
		
		public static bool isNeutral(Expression ex)
		{
			if (ex is System.Qizx.XQuery.Fn.Error.Exec)
				return true;
			// or empty sequence:
			if (!(ex is SequenceExpr))
				return false;
			SequenceExpr sex = (SequenceExpr) ex;
			return sex.exprs == null || sex.exprs.Length == 0;
		}

        public static bool isVacuous(Expression ex) {
            return ex != null && ex.isVacuous();
        }
		
		public override XQType getType()
		{
			return base.getType(); // TODO
		}
		
		public override void  Dump(ExprDisplay d)
		{
			d.header(this);
			d.property("mode", mode);
			if (what != null)
				d.child(what);
			if (where != null)
				d.child(where);
		}
		
		public override Expression StaticCheck(ModuleContext context, int flags)
		{
			if (what != null)
			{
				what = context.staticCheck(what, flags);
			}
			if (where != null)
			{
				where = context.staticCheck(where, flags);
			}
			return this;
		}
	}
}